An organic light emitting diode (OLED) has advantages of rapid response, gorgeous color, being light and convenient, broad work scope, and so on. The OLED has been a new star in display industry. As low temperature poly-silicon (LTPS), commonly-used in current OLED display panel, has disadvantages of complicated process, expensive cost, difficulties in being large-sized, thus a backplane of metallic oxide TFT (metallic oxide thin film transistor) has been an important direction focused by OLED research and manufacture.
Although the metallic oxide TFT has an excellent performance with a simple manufacturing process and being easy to be large-sized, the metallic oxide TFT has a poor photo-stability, which has long perplexed manufacturers. Currently, there is still no method for properly solving the photo-stability of the metallic oxide TFT in the OLED display panel. Particularly, in a bottom emitting OLED display panel as shown in FIG. 1, a light-ray (shown as arrows), generated by an electroluminescence of an organic light emitting layer 14, will directly irradiate or reflect to a thin film transistor (TFT) structure unavoidably, an incident visible-light generates a negative influence on performances of the thin film transistor (TFT), such as output/transfer capacity and reliability, the shorter wavelength of the incident visible-light, the more significant of a drift of the thin film transistor (TFT), and at the same time, a smaller switch ratio and an increasing current of drain electrode directly influence a display performance of a display product.